When I was using the hanna checker last yr, I would test 2x in a row Occasionally, and I did see significant differences maybe twice. I am always careful on quantities and to clean the vial very well before each test. I decided it was too inconsistent to serve my needs and why I back shelved it. During my tests I'm doing this time I was not double testing, but I will now because reagent is almost exprired anyway so in the name of my pseudoscience well make use of it best we can. For the below tests I am not doing an other additions at all that would likely effect daily ALK other than KALK ATO. ALK dose is on pause till I reach <8.7 and I am diluting my 100 gallon KALK ATO because it was introducing more ALK than my systems is using and my CA is rather high "470" atm and I want to let the ATO water dilute so I may get those back into line over the next 30 days. This is typical of my system and I would not say I have a huge ALk consumption rate in my system. I do find I over shoot ALk if my KALK is fully saturated due to over 4 gallons a day going into the system for evaporation. To be as fair as possible to HANNA checker I am rinsing both with room temperature RODI prior to test and after the test which is typical for all my test vials and test procedures including salifert. I use the same glass vial each time in the checker as well. I don't use the second vial they provide. lid is on every time and vial is wiped clean every time. All of those things I think can matter and lead to inconsistency in all testing methods.
results to date=
3-2-18 check =
8:30 am =salifert 9.3/ Hanna 9.3
5:30 pm = salifert 9.3/ Hanna 9.3
3-3-18 checks
8:30 am =none
5:30 pm =none
3-4-18 am test
9:30 am =first test salifert =8.9,/Hanna 9.0/ second Hanna =9.1,
Pm test TBD